The present invention relates to a resonator for internal combustion engines and, more specifically, to a resonator having a plurality of resonant frequencies.
The conventional type resonator 100 of FIG. 1 being located in an intake duct 13, consists of a predetermined closed volume or chamber 17 to which is connected a tubular member 15. The resonant frequency Fp of this type resonator is calculated as follows: ##EQU1## wherein, D is an inside diameter of the tubular member 15, l is a length of the tubular member 15 and V is the volume of the resonant chamber 17. It has been observed that in the conventional type resonator, dimensions of each component cannot be varied freely. Therefore, the resonant frequency is discriminately determined from such dimensions so that a reduction of an intake noise is achieved only at a specific resonant frequency, thus satisfactory reduction of the intake noise over a wide range of engine speeds is impossible to achieve.